For industrial tablet computers, we often see some interfaces, such as COM (serial port), LAN (network port), VGA (display data interface), HDMI (high definition display data interface), USB, DC (power interface), AUDIO (headphones) ), MIC (microphone) and some old-fashioned PS/2 (mouse keyboard interface) and so on. We collectively refer to these industrial panel computer interfaces as IO interfaces.
I means INPUT (input), O means OUPUT (output), and IO interface is the interface of some input or output. The input is the signal or data received by the system, and the output is the signal or data sent from it.
The function of the IO interface is to connect various types of peripherals with the industrial panel computer CPU to form a complete microcomputer hardware system through the IO interface. Used for data exchange, processing and storage.
What are the main types of information exchanged between CPU and peripherals (IO) of industrial tablet PCs?
The information exchanged between the host and the IO device can be divided into three categories: data information, status information and control information.
1) Data information
Data information is divided into three forms: digital, analog and switch.
1. Digital quantity
The digital quantity is the data that the industrial tablet computer can send, receive and process directly. For example, the information exchanged with the CPU by I/O peripherals such as keyboards, monitors, printers, and disks.
2. Analog
When an industrial panel computer is used in a control system, the input information is generally a continuously changing physical quantity from the field, such as temperature, pressure, flow, displacement, humidity, etc. These physical quantities are processed by sensors and amplified to obtain analog voltage or current. These analog quantities must be converted from analog to digital (A/D conversion) before they can be input to the industrial panel computer. Conversely, the control signals output by the industrial panel computer are all digital, and they must be converted from digital to analog (D/A conversion) before they can control the scene by converting the digital to analog.
3. Switch quantity
The switch quantity can represent two states, such as the opening and closing of the switch, the running and stopping of the machine, the opening and closing of the valve, etc. These switching quantities usually need to undergo corresponding level conversion to connect with industrial panel computers.
2) Status information
The status information is used as the contact information when exchanging data between the industrial tablet PC CPU and peripherals, reflecting the current working status of the peripherals, and the peripherals are sent to the CPU through the interface. The CPU can know whether the data of the input device is ready and whether the output device is idle by reading the peripheral status signal. For input devices, the level of the ready (READY) signal is generally used to indicate whether the data to be input is ready; for output devices, the level of the busy (BUSY) signal is used to indicate whether the output device is in an idle state. If it is an idle state, Then you can receive the information output by the CPU, otherwise the CPU will suspend sending data. Therefore, the status information can ensure the correct data exchange between the CPU and peripherals.
3) control information
The control information is transmitted by the CPU to the peripheral through the interface, and the CPU sets the working mode of the peripheral (including the interface) and controls the work of the peripheral by sending the control information. For example, the start signal and stop signal of the peripheral are common control information. In fact, control information often has different meanings depending on the specific working principles of peripherals.
Although the meanings of data information, status information, and control information are different, in a microcomputer system, when the CPU exchanges information through the interface and peripherals, it can only use input instructions (IN) and output instructions (OUT) to transmit data, so the status Information and control information are also transmitted as data information, that is, state information is used as input data, and control information is used as output data. In this way, state information and control information are also transmitted through the data bus. But in the interface, these three kinds of information are stored in different registers.
The IO interface function of the industrial tablet computer is related to the operation and exchange of the entire machine information. Generally speaking, the IO interface of an industrial tablet computer can be customized and developed according to customer needs to meet different customer application machines and application scenarios.
